1. Field of the Invention
The present invention relates to a portable terminal device such as a cellular phone, a digital phone, a Personal Digital Assistant (PDA), a Hand Held Phone (HHP), a notebook computer, a Palm PC, or a Tablet computer, which necessarily requires a data display unit, and more particularly to a portable terminal device, which employs a display unit utilizing holographic technology.
2. Description of the Related Art
In general, a portable terminal device is a portable device which performs wireless communication with a base station, thereby enabling a user of the device to communicate with another person. Portable terminal devices can be classified into various types according their shapes or functions, or the locations of the human body at which they are carried. According to their shapes, the portable terminal devices may be classified into portable terminal devices of the bar type, flip type, folder type, flip-up type, and folder type usable for both PDA and mobile phone. Further, according to their functions, the portable terminal devices may be classified into devices for voice communication, image communication, Internet surfing, Internet games, and chatting. Further, according to the locations of the human body at which they are carried, the portable terminal devices may be classified into around-the neck types, around-the wrist types, and in-the-pocket types.
All the portable terminal devices as described above must have an antenna, a data input/output means, and a data transmission/reception means, in order to perform the communication function. In general, a keypad or a touch sensitive panel is employed as the data input means. In this case, a user can input data by pressing desired keys among a plurality of keys arranged on the keypad or by touching the touch sensitive panel. As the data output means, a display unit such as an LCD module is generally used. Further, the data transmission/reception means generally includes a microphone and a speaker.
Existing portable terminal devices generally employ a display system known as an LCD which stands for a liquid crystal display, in order to optically display various data or information. In a typical LCD, a liquid crystal layer is sandwiched between two transparent glass plates, and polarizer plates are each attached to each outer surface of the upper and lower transparent glass plates. Further, a reflection sheet may be attached to the bottom of the lower polarizer plate. An LCD provided with the reflection sheet is called a reflection LCD, while an LCD provided with no reflection sheet is called a projection LCD. The construction of the existing LCD as described above can be easily understood by those related in the art.
However, the conventional LCD which has been widely used as a display system in the prior art is relatively wide and thick, which impose restrictions on the size-reduction of a portable terminal device. Especially, in the case where the LCD and a main printed circuit board mounting various circuit elements thereon are mounted to different housings such as a terminal housing and a folder housing, a portable terminal device must inevitably employ electric wires or flexible printed circuit board (FPCB) capable of establishing electric connection between the LCD and the main printed circuit board, thereby enabling signal transmission between the LCD and the main printed circuit board. In this case, the electric connection as described above may be easily broken when the portable terminal device is dropped or impacted. Moreover, since rotational force is usually applied to the connection elements, the breaking of electric connection as described above is a severe problem in the existing portable terminal device.